With the drastic increase in energy use by humans, the demand for production of energy to be used is simultaneously increasing. Although energy is produced from nuclear power plants, which are currently the most widely used among various energy production methods, there is, on the other hand, real concern about the risk of using nuclear power plants and the effect of waste thereof on the environment. In contrast, solar light gives the earth considerable energy without environmental pollution or risks associated with the use thereof, but humans have not yet become able to utilize most such energy.
Recently, as the exhaustion of existing energy resources is expected, interest in alternative energy sources to replace them is increasing. Among them, a solar cell is receiving attention as a next-generation power source that directly converts solar energy into electrical energy using a semiconductor device.
The most basic structure of a solar cell is a diode composed of a PN junction, and solar cells may be classified into crystalline (monocrystalline, polycrystalline) wafer-type solar cells and thin-film (amorphous, polycrystalline) solar cells depending on the material of the light absorption layer.
A solar cell typically includes a solar cell module, configured such that a solar cell element, such as silicon, gallium-arsenic, a copper-indium-selenide (CIS)-based compound, a copper-indium-gallium-selenide (CIGS)-based compound, or a CdTe compound, is protected with an upper transparent protection member and a lower substrate protection member and such that the solar cell element and the protection member are fixed using an adhesive sheet.
In the solar cell module, the upper transparent protection member is typically glass, that is, cover glass, but the glass reflects solar light, undesirably deteriorating the power generation efficiency of the solar cell module. Accordingly, many attempts have been made to form an anti-reflective film on the solar cell module using an anti-reflective coating solution composition. Such an anti-reflective film is able to form a low-refractive-index layer, and thus properties such as low reflectance, high transmittance and high durability are required.
Meanwhile, when glass having a predetermined pattern is located on the outermost surface of the solar cell module, the amount of solar light that is incident on the solar cell module may be increased, compared to when glass having no pattern is used. Recently, developed are techniques in which an anti-reflective coating film is formed on the surface of the glass opposite the surface having a pattern to thereby further increase the amount of solar light that is incident on the solar cell module. When an anti-reflective coating film is used, transmittance may be expected to be increased by about 3% compared to when no anti-reflective coating film is used.
However, the anti-reflective coating film having high transmittance exhibits poor durability, making it difficult to maintain the initial transmittance thereof. On the other hand, an anti-reflective coating film having good durability may manifest poor transmittance.
Thus, there is a need to develop an anti-reflective coating solution composition in which a refractive index is lowered to thus increase transmittance and in which durability such as abrasion resistance is superior.
With regard to the anti-reflective coating solution composition having a low refractive index and high durability, such as abrasion resistance, in order to increase the solar cell module efficiency, Korean Patent No. 1021659, entitled ┌Method of preparing coating solution for increasing light transmittance in order to serve for solar cell module glass and coating solution composition prepared thereby┘, discloses a method of preparing a coating solution that is able to increase light transmittance in order to serve for a solar cell module glass, the method including the first step in which 0.05 g of brij-56 (poly(oxyethylene) nonionic surfactant) and polyvinylpyrrolidone are added to give aluminum alkoxide having high reactivity, to which an aggregation inducer that causes a sol-gel reaction is then added, whereby aggregation is induced through a sol-gel reaction, thus forming particles having a size of 100 nm to 500 nm. Moreover, Korean Patent No. 0737131, entitled ┌Low-refractive-index-layer coating solution for anti-reflective film and anti-reflective film using the same┘, discloses an anti-reflective film having superior properties, such as a low reflective index and high visible light transmittance, which includes a fluorinated compound, prepared by substituting the crosslinkable portion of an existing fluorine-based acrylic and methacrylic resin with fluorine so that the fluorine content of a cured product after a coating process may be increased.